Important submarine canyon ecosystems at risk

A NIWA scientist is calling for greater protection of submarine canyons around New Zealand as their rich marine life comes under increasing threat from human activity.

Marine ecologist Dr Ashley Rowden is the co-author of a new paper published in the scientific journal Frontiers in Marine Science.

A team of scientists has reviewed recent studies of submarine canyons around the world. The team is part of INCISE – the International Network for submarine Canyon Investigation and Scientific Exchange, an initiative that aims to bring together scientists working on all aspects of submarine canyon research.

Submarine canyons are major features of continental margins. There are about 10,000 large canyons around the world with at least 230 off New Zealand.

Dr Rowden said recent projects focused on the study of canyons, have considerably increased our understanding of their ecological role, the goods and services they provide to humans, and the impacts human activities have on their overall ecological condition.

Pressures from human activities include litter, fishing, dumping of land-based mine tailings, and oil and gas extraction. The effects of climate change may modify the intensity of currents within canyons, which is predicted to impact the structure and functioning of canyon communities, as well as affect food supply to the deep-ocean ecosystem.

Only 10 per cent of canyons worldwide are covered by marine protected areas (MPAs), and these are not evenly distributed around the globe.

In addition, canyon protection is mainly focused on the shallow areas, and Dr Rowden says it is important to protect complete systems as they act as the main connection between shallow and deep waters.

Canyons faced a number of conservation issues, and the review included what research was needed to inform management measures to protect canyon ecosystems.

“MPAs within the New Zealand Exclusive Economic Zone protect 41 large canyons, or 17 per cent of their total estimated area, but more should be part of the network. They contain important biodiversity and face a number of threats,” Dr Rowden says.

Most of the Kaikoura Canyon is included in the Hikurangi Marine Reserve, which was designated a protected area in 2014. This canyon has one of the most productive deep-sea ecosystems in the world.

Dr Rowden says the effect of the November earthquake on the deep-sea ecosystem in the canyon is not yet known, and research is required to understand the impact submarine landslides and sediment-laden currents may have had on its biodiversity.

“We need to know whether the canyon is still operating effectively as a marine reserve.”

The review has identified the ecological importance of canyons, and also highlighted the need for better understanding of the human impacts on canyon ecosystems.